Generic internal combustion engines with bottom camshafts (OHV arrangement) and hydraulically variable valve actuation based on the so-called lost motion principle in which the transmission of the cam lift to the gas exchange valve is infinitely variable through the variable-volume pressure chamber disposed between the master piston and the slave piston, are known, inter alia, from US 2004/0065285 A1 and U.S. Pat. No. 6,694,933 B1. In the internal combustion engines disclosed therein, the bottom camshaft is mounted directly in the crankcase. In the case of internal combustion engines with a very large volume (for example marine engines), it is also usual to mount the bottom camshaft in a camshaft housing made separately from the crankcase.
In opposition to the excellent thermodynamic potential of hydraulically variable valve actuation as compared to standard-type valve actuation without lift variability, however, is the considerably higher system complexity which necessitates correspondingly vast construction and manufacturing modifications to the hydraulic valve actuation of an existing engine architecture. The concomitant complexity of manufacturing and the cost increase are particularly high if the otherwise identical internal combustion engine has to be constructed with and without hydraulically variable valve actuation.